This invention relates generally to a shuffle device, and more particularly, to an optical fiber separation and regrouping device for an optical shuffle.
Optical fibers provide a well-known medium for conveying information in data and communications systems, such as computer and telephone systems. It is well known, that optical fibers possess characteristics wherein their light transmission capability is greatest when the fiber is straight and devoid of bends, and that they are subject to signal attenuation due to bending. These bending losses can be characterized as losses due to larger, gradual bends (macrobends), and losses due to much smaller and sharper bends (microbends). Macrobends can result from winding the fiber, for example, while microbends arise because of random variations in direction of the core axis.
Optical fibers, therefore, are typically provided with protective coatings to preserve the inherent strength of the glass and to buffer the fiber from microbending induced attenuation. Individual optical fibers can be encapsulated in a polymer casing that protects the fiber from damage, or an optical fiber ribbon can be formed by aligning a plurality of optical fibers in a linear array and then encapsulating the fiber array in a polymer casing to form the ribbon.
Two coatings are generally used to form a fiber optic cable or ribbon. The first coating, which is typically applied to the surface of the optical fiber, is generally referred to as the primary coating. The primary coating, once cured, is a soft, rubbery material that serves as a buffer to protect the fiber by relieving the stress created when the fiber is bent. The primary coating usually has a low glass transition temperature to provide resistance to microbending.
Certain characteristics are desirable for the primary coating. For example, the primary coating must maintain adequate adhesion to the glass fiber during thermal and hydrolytic aging, yet be strippable for splicing purposes. The modulus of the primary coating must be low to cushion and to protect the fiber by relieving stress on the fiber, which can induce microbending and, consequently, inefficient signal transmission. It is desirable for the primary coating to have a low glass transition temperature to ensure that the coating remains in a rubbery state throughout a broad temperature range.
The secondary or outer coating is applied over the primary coating. The secondary coating functions as a hard, protective layer that prevents damage to the glass fiber during processing and use by providing desired resistance to handling forces, such as those encountered when the coated fiber is cabled.
Additionally, it is often desirable to switch information between systems that use optical fibers as information conveyance media. This can be accomplished by directing the optical fibers output from each system into one or more systems. This is known as shuffling the fibers, and the mechanism by which this is accomplished is known as an optical shuffle. An optical shuffle in which one fiber output from each system is directed to a different system is known as a perfect shuffle. Thus, in a perfect shuffle, each system can communicate with every other system.
One way by which an optical shuffle can be formed is to strip the coatings from the fibers or ribbons inputted to the shuffle, and then xe2x80x9cre-ribbonizexe2x80x9d the exiting fibers. That is, the stripped fibers can be grouped differently, re-encapsulated, and then output from the shuffle. Thus, a discontinuity is created in the area of re-ribbonization, and the fibers can remain undesirably exposed in that region. Moreover, the fibers are prone to strain and bending in the area of the discontinuity.
There is a need in the art for a compact optical shuffle that permits re-ribbonization of a plurality of optical fibers, while protecting the fibers from damage and reducing strain and bending in the discontinuity. It is an objective of the present invention, therefore, to provide an optical fiber separation and regrouping device that protects and controls bending of the optical fibers at the discontinuity.
The present invention is a separation and regrouping device comprising a housing and a plurality of conductive elements, such as optical fibers, extending through an interior region of the housing. The optical fibers can be encapsulated individually as fiber optic cables, or grouped together and then encapsulated to form optical fiber ribbons.
Each optical fiber has a first coating disposed along a first portion thereof, and a second coating disposed along a second portion thereof. An encapsulation discontinuity is formed on each optical fiber between the first coating and the second coating. The housing can be pre-assembled or molded over the optical fibers to contain the optical fibers and surround the encapsulation discontinuities.
The interior region of the housing can include a guide channel that channels the optical fibers through the interior region of the housing. The guide channel can be a single channel, or can include a plurality of channels. The guide channel can also be twisted to rotate the fibers as they extend through the housing.
The device can also include one or more strain relief elements within the interior region of the housing that contain the optical fibers and surround the encapsulation discontinuities. A single strain relief element can contain a plurality of fibers, or the device can include a plurality of strain relief elements, each of which contains a single fiber.
To further reduce strain on the conductive elements, the housing can also include one or more potting chambers in which the optical fibers can be potted to the housing.
A method according to the invention for organizing conductive elements includes providing a plurality of conductive elements arranged in first groups, separating the first groups into individual conductive elements, and rearranging the individual conductive elements into second groups.
The first groups can be optical fiber ribbons, which are separated by unribbonizing the fibers (e.g., by stripping the encapsulation from the ribbon to expose the fibers). The unribbonized fibers can then be re-ribbonized (i.e., rearranged into a second group and encapsulated to form a second ribbon).
Thus, a method according to the invention for managing a plurality of conductive elements includes arranging a first section of the conductive elements in a first arrangement, arranging a second section of the conductive elements in a second arrangement, and enclosing a third section of the conductive elements located between the first and second sections.
The third section of the elements can be enclosed by inserting the conductive elements in a pre-assembled shuffle device, or by encapsulating the conductive elements such as by overmolding a housing over the third section, or by potting the third section within a tubular structure.